Extrusion is a known economical and widely used method of processing an elastomer for forming unvulcanized rubber coumponds.
An extruder generally comprises a cylindrical piece or barrel in which a screw is rotating. An elastomer strip introduced into the extruder is seized by the screw whose threads advance it toward the end of the cylinder, which has a die of the disired shape. Unvulcanized rubber compounds, heated by processing and ejected under pressure, have the desired continuous shapes. One example is a tire tread, which leaves the extruder flat, is then cut up to proper lengths, and assembled on the drum of the tire building macahine which other "green" tire components. A great variety of rubber components can be made by extrusion using the same essential components. The same basic system is used but the die is changed to alter the configuration of the extruded product. Accordingly, the prompt exchange of a die holder is very important for improvement of productivity of rubber goods.
As shown in FIGS. 1 and 18, an extruder having a movable clamp 1 and a recess 2 on the die head portion 3 hereof will retain a die holder 4. However, it takes a significant amount of time to move a die holder 4 from the point of insertion into an operative location, denoted as element 5 between the recess 2 and the clamp 1. This is because removing an existing die holder and setting a new preheated die holder is conventionally done from the same direction. It is not only difficult but is also dangerous to exchange a die holder using a jig crane as is conventional. The remaining structure of the extruder will be explained herein. Reference is also made to U.S. Pat. No. 4,358,261 which describes a multi-extrusion die system with interchangeable die holders.